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Factors affecting Drug action PowerPoint Presentation

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Description : Factors affecting Drug action

Tags : Dosing

Published on : Mar 21, 2018 | Views : 11313 | Downloads : 32

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Slide 1-

Factors affecting Drug action or Factor modifying drug effect Age Body weight Sex Time of administration Route of administration Drug interaction Tolerance Idiosyncracy Nurtitional status Therapeutic index Presence of disease
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1. Age Drug should be given according to age. Different age group are referred as Neonates: 1-30 days Infants:-upto 1 year Children:- 1-12 years ( small children-1 to 5 years and big children 6-12 years) Adolescence :- 12-18 years Adult:- 18-60 years Elderly:- above 60 years
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In children, infant and neonates special care is needed while calculating dose as hepatic system, renal system and enzyme system is not properly developed in them. They differ from adult in their response to drugs Children dose may be calculated from adult dose by using age, body weight or body surface area
Slide 4-

According to body weight: Individual dose =Children body weight(kg) X average adult dose 70 According to body surface area Individual dose = BSA (m2) X average adult dose 1.7 Young’s formula: According to age Child dose = age X adult dose age + 12
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2. Body weight Body weight also affect the dose of drug Those having more body weight require high dose while those with less bodyweight require low dose Generally female has smaller body weight so they require less amount of drugs.
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3. Sex It is another factor affecting dose of drug Pregnancy, lactation are some condition related to sex in which drug administration and dose should be considered carefully. Drug which crosses placenta shouldnot be given during pregnancy. Uterine stimulant drugs shouldnot be given during pregnancy Similarly drugs which are secreted in milk shouldnot be given to breast feeding women.
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4. Time of drug administration Some drug should be administered in empty stomach. Like PPI Some drug should be used at night time to reduce its side effects. Like cetrizine
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5. Route of administration Route of administration affects the absorption of drugs Like IV dose have 100% bioavailability Similarly sublingual route has high absorption then other oral dose Too rapid I.V. administration causes sudden fall in blood pressure. Change of route of drug administration may produce qualitative change
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For example Magnesium sulphate when given orally is cathartic but parenterally it produces depression of CNS
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6.Tolerance It is a reduced response of a drug on repeated administration. As a result of tolerance larger and larger dose have to be given to obtain the original response. It is a phenomena of cellular adaptaion to a foreign chemical induced by repeated administration.
Slide 11-

7. Idiosyncrasy It is a personal pecularity. It is due to genetic and physiological cause of particular person. So particulr individula may have different response to the drugs than general people. So drug dose must be individualise.
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8. Drug interaction Effect of one drug is influenced by simultaneous adminstration of another drugs. Different types of drug interaction are Additive effects Synergistic effect Antagonistic effect
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Additive effect :-when combined effect of two drugs is equla to the sum of their individual effect it is called additive effect It is seen when 2 drugs having identical MOA are combined Eg:-Ibuprofen + paracetamol Salbutamol + Aminophylline
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Synergistic effect When the combined effect of two drugs is more than the sum of their expected individual effect it is called synergistic effect. 1+1=3 Here action of one drug is increased by another It occurs when 2 drugs produce same effect by different MOA. Hydrochlorthiazide+ atenolol Amlodipine + atenolol Metformin + Glimeperide
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Antagonistic effect When one drug decreases or inhibits the action of another drug they are called antagonistic effect. Effect of(1+2)< effect of 1 + effect of 2
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9. Therapeutic index It is the index for the safety of drug. Larger the therapeutic index safer will be the drug and high dose can be give like penicillin, NSAID Smaller the Therapeutic index lower the safety margin of drug. Hence smaller dose should be given like digoxin.
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10. Presence of disease NSAID shows its effect only when there is pain, fever and inflammation in body. Some drugs are effective only in disease condition. While diazepam show sedattion effect in normal as well as disease condition So some drugs are effective in normal as well as disease condition
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11. Nutritional status Malnutrition may lead to decrease in drug metabolising enzyme